This study is a double-blind, placebo-controlled trial of calcium carbonate supplementation of diet to a total of 1500 mg of calcium per day in healthy men 65 years of age and older. The trial enrolled men with bone mineral density of the femoral neck or trochanter of one standard deviation below to one-half standard deviation above age-matched controls, and a daily calcium intake of 1000 mg per day or less. Patients were followed every three months with bone mineral density measurement of the hip and lunbar spine taken at baseline and at one and two years.